Ink jet head with nozzle arrangement to reduce viscous drag

ABSTRACT

A nozzle arrangement structure in an ink jet print head. A plurality of pressure chambers are arranged in circular form, and a plurality of nozzles receive an ink supply from the corresponding pressure chambers and are arranged in an zig zag arrangement to obtain a small interval between the dots. Two straight lines concerning the zig zag arrangement are inclined against a printing direction and a direction perpendicular to the printing direction. When an ink discharge from the nozzles is controlled, preprocessing of serial data is carried out by hardware.

BACKGROUND OF THE INVENTION

i) Field of the Invention

The present invention relates to an ink jet print head for use in anon-impact printer, and more particularly to its nozzle arrangementstructure and also to a head driver circuit for the ink jet print headon the premise of the nozzle arrangement structure.

ii) Description of the Related Arts

Conventionally a non-impact printer using an ink jet print head has beenknown. The non-impact printer can be widely used for a facsimilemachine, a plotter, a bar code printer, a digital copying machine andthe like. The non-impact printer is provided with a head having a numberof fine nozzles, and by blowing fine particles of an ink onto printingmedium such as paper or the like from the nozzles, printing is carriedout without contacting the head with the printing medium.

In an impact printer for performing printing by contacting a head with aprinting medium, when the head is designed, it is necessary to considera material of the printing medium, and also, when the head is produced,it is required to sufficiently consider the same. The non-impact printerhas an advantage that such a technical limitation does not exist.Further, high speed printing is possible by using the non-impactprinter.

In FIG. 32, there is shown a conventional ink jet print head. This inkjet print head 10 has a similar construction to one disclosed inJapanese Patent Laid-Open No. Hei 2-266944.

The ink jet print head 10 possesses a flat plate structure. This flatplate structure can be formed by etching a glass plate or the like. Theink jet print head 10 is comprised of an ink chamber 12, a plurality ofpressure chambers 14, a plurality of ink slits 16 and a plurality ofnozzles 18. The ink chamber 12 is formed in circular shape near theperipheral part of a circular glass plate. The pressure chambers 14 areformed inside the circle. The pressure chambers 14 are formedcorresponding to the respective nozzles 18. The ink slits 16 couple thepressure chambers 14 with the corresponding nozzles 18. The nozzles 18are arranged in a rhombic form near the center of the ink jet print head10, as shown by a one-dotted line in FIG. 32. In fact, the fine nozzles18 are arranged on this rhombic form in high density, but this isomitted for brevity in FIG. 32.

In the ink jet print head 10, as a member to be overlapped on this flatplate structure, a pressure generating part 20 is used. The pressuregenerating part 20, for example, is composed of a piezoelectricsubstrate or the like, and on this pressure generating part 20, aplurality of electrodes 22 are formed. Each electrode 22 is providedcorresponding to each pressure chamber 14 so as to construct a singlepiezoelectric element. Hence, when an electric signal is applied to oneelectrode 22, the piezoelectric element of this electrode 22 is excited,and the pressure is added to the corresponding pressure chamber 14.Then, the ink in the pressure chamber 14 is caused to flow in thedirection to the nozzle 18 via the ink slit 16. As a result, the ink isdischarged from the corresponding nozzle 18. In this case, the pluralityof electrodes 22 can not be seen in the state that the pressuregenerating part 20 is partly cut out, as shown in FIG. 32, but the rowof the plurality of electrodes 22 is shown by two broken lines forunderstanding.

In the ink jet print head, the viscous drag of the ink flowing in theink slit depends on the length of the ink slit. In this conventionalexample, since the pressure chambers 14 are arranged in the circularform, the lengths of the ink slits 16 become almost equal. Hence, in theconventional example, the viscous drags of the ink slits 16 areequalized to obtain effects such as a realization of high frequencydriving and the like.

However, when the pressure chambers 14 are arranged in the circular formas described above, since the nozzles 18 are concentrated upon thecentral part of the circle, it is difficult to perform multi-dotprinting. The dot is a printing part formed by the ink discharged oncefrom one nozzle. In the conventional example shown in FIG. 32, since theinterval between the adjacent nozzles 18 is restricted by the intervalbetween the ink slits 16, the interval between the nozzles 18 becomeslarge, and as a result, the dot interval becomes large.

SUMMARY OF THE INVENTION

It is the first object of the present invention to make the dot densityhigh and thus to make possible clear and fine printing.

It is the second object of the present invention to reduce the viscousdrag of the ink without increasing the difficulty of manufacturing andthus to realize high speed printing with high accuracy.

It is the third object of the present invention not to necessitatepreprocessing such as an order operation and the like on driving datawhen an ink jet print head improved by the present invention is driven.

An ink jet print head of the present invention comprises:

a) a plurality of nozzles arranged in a zig zag arrangement on a flatsurface for discharging ink; and

b) discharge means for causing the discharge of the ink from thenozzles.

It will be readily understood that the main improvement of the presentinvention is in the arrangement of the nozzles. At the same time, itwould be incorrect to consider that this improvement is only a designchoice or an obvious modification for those skilled in the art or thelike. First, though the above-described subject, that is, a high densityarrangement of the nozzles has been widely recognized for those skilledin the art, an effective and readily practicable solving method has notheretofore been known. The present invention is completed inconsideration of some already proposed improved constructions and undersufficient and careful consideration, and this proposal is by no meansan obvious modification for those skilled in the art. Second, thearrangement of the nozzles of the main improvement of the presentinvention requires remarkable regularity, and from this viewpoint thepresent invention is by no means the proposal of the obviousmodification for those skilled in the art.

The zig zag arrangement is an arrangement satisfying the following twoconditions. That is, first, the nozzles are arranged on first and secondstraight lines positioned on the flat surface. Second, the nozzlesarranged on the first straight line are offset with respect to thenozzles arranged on the second straight line along a directionperpendicular to a printing direction.

The first advantage of the zig zag arrangement is that while theinterval between the adjacent nozzles is determined to be relativelylarge, the dot density can be increased, and thus the printing qualitycan be improved.

In the case of a conventional rhombic arrangement, the nozzles on eachedge of the rhombus are arranged on one straight line, and ink pathscorresponding to the nozzles are formed in one side of the straight line(outside the thombus). Hence, it is required that the interval betweenthe adjacent nozzles is at least the sum of the width of the ink pathand the thickness of the partition wall between the ink paths.

On the other hand, in the zig zag arrangement of the present invention,the nozzles are arranged on the first and second straight linesseparated from each other. Hence, the above-described intervalrestriction (at least the sum of the width of the ink path and thethickness of the partition wall between the ink paths) applies for everystraight line. If the adjacent two nozzles are arranged on differentstraight lines, such an interval restriction does not apply, and anextremely loose interval restriction such as at least the thickness ofthe partition wall between the nozzles applies instead.

In the present invention, first, since the nozzles are arranged on theseparated two straight lines, the ink paths are not drawn out to oneside of the nozzle arrangement, and the ink paths can be alternatelydrawn out to both sides of the nozzle arrangement. Second, since thenozzles arranged on the first straight line are offset with respect tothe nozzles arranged on the second straight line along the directionperpendicular to the printing direction, the adjacent nozzles are notarranged on the same straight line but on the different straight lines.In other words, the adjacent nozzles adjoin each other slantinglyagainst the two straight lines.

In this manner, according to the present invention, while the intervalbetween thee nozzles is actually kept relatively large, the intervalbetween the nozzles can be reduced. Thus, the aforementioned firstadvantage can be obtained.

The second advantage of the zig zag arrangement, that is, the reductionof the viscous drag of the ink is generated on the basis of the firstadvantage. For example, since the interval restriction of the nozzles isextremely loose, the ink inlet dimension of the nozzles can be enlarged,and the cross section of the ink paths corresponding to the nozzles canalso be enlarged. This all lead to a reduction of the viscous drag.

For example, when the internal shape of the nozzles is formed to atapered shape tapering from the ink inlet side to the ink outlet side,the tapered angle can be enlarged compared with a conventional nozzle.This shows that the ink outlet dimension is not changed or the same asis conventional, but the ink inlet dimension can be enlarged. In oneembodiment described hereinafter, it is described that this angle is atleast 4° against the ink discharge direction, and the ink inletdimension/the ink outlet dimension is at least 2.5. Attention should bepaid to this fact. However, of course, the present invention is notrestricted to this angle.

Also, for example, when the internal shape of the nozzles is formed to astepwise shape, that is, the diameter size is stepwise changed, the inkoutlet dimension is the same as conventional, and the ink inletdimension can be enlarged. For instance, the ink inlet dimension can beat least 3 times of the ink outlet dimension.

Further, the depth of the ink paths can be enlarged more than its width,within the limit of thickness of glass, at least near the nozzles byusing anisotropic etching. By this, the cross section of the ink pathcan be enlarged. This means, at the same time, that the viscous drug ofthe ink path can be further reduced, and the interval between the inkpaths can be reduced. On the other hand, the above-described firstadvantage of loosening the restriction of intervals of ink paths alsoallows loosening of the restriction of widths of ink paths. That is, thesetting of the depth of the ink path, along with the above-describedfirst advantage, makes the dot density large.

The third advantage of the zig zag arrangement, that is, theequalization of the viscous drag is also produced on the basis of thefirst advantage. As described above, there is caused room for enlargingthe width of the ink path, and this, at the same time, make possible adesign so as to remove the viscous drag difference between the ink pathscorresponding to the nozzles.

More specifically, by relatively diminishing the cross section of theink slits concerning the nozzles arranged in relatively end portions ofthe first and second straight lines, and by relatively enlarging thecross section of the ink slits concerning the nozzles arranged near thecentral portions of the first and second straight lines, the viscousdrags of the ink slits can be equalized.

This advantage becomes remarkable when the nozzles are arranged so as toconcentrate at the portion near the central point of a circle or acircular arc and further the ink paths are formed so as to draw analmost radial pattern from this central portion. That is, although sucha radial construction itself is already known, by combining with the zigzag arrangement of the present invention, the above-described thirdadvantage can be made more remarkable.

The fourth advantage of the zig zag arrangement is that the drivingforce of the nozzles can be reduced. This is based on theabove-described second advantage. That is, when the viscous drag isreduced, it is possible to reduce the energy (driving force of thenozzles) required for supplying the ink to the ink paths.

The discharge means for discharging the ink by driving the nozzles, forexample, can be constructed by using piezoelectric elements. Each of thepiezoelectric elements is excited and caused to distort by a commandsupplied as a voltage. When the piezoelectric element is used as thedischarge means, it is preferable to use a diaphragm member vibrated bythe distortion of the piezoelectric element. When the viscous drag isreduced in the zig zag arrangement, as described above, since thevoltage for driving the piezoelectric element can be lowered, thedamping oscillation becomes quick to improve the response of the inkdischarge operation. This enables high speed printing.

The ink jet print head of the present invention can be constructed as aflat plate structure. This flat plate structure includes:

a) a substrate;

b) a plurality of nozzles arranged in a zig zag arrangement on thesurface of the substrate as the flat surface; and

c) path means formed on the substrate for supplying the ink to thenozzles.

The path means is means corresponding to the above-described ink path.This, for example, can be constructed by a plurality of ink slits formedon the substrate so as to connect to the corresponding nozzles; aplurality of pressure chambers formed on the substrate corresponding tothe ink slits so as to connect to the ink slits; and an ink introducingmechanism for introducing the ink into the pressure chambers. When thepath means is formed in such a construction, the discharge means isconstructed to include a plurality of pressing elements attached on thesubstrate corresponding to the pressure chambers so as to apply thepressure to the corresponding pressure chambers depending on thecommand. Also, the ink introducing mechanism, for example, can beconstructed to include an ink chamber formed in the position so as tosurround and connect to the pressure chambers; and an ink introducingaperture for introducing the ink into the ink chamber.

In this construction, the ink discharge operation is as follows. First,the pressing element receiving the command applies the pressure to thecorresponding pressure chamber. In response to this, the ink within thepressure chamber is fed to the corresponding ink slit. When the ink isfed to the ink slit, the ink is discharged from the correspondingnozzle. When the command is released, the ink of almost the same amountas the amount fed to the ink slit is introduced into the pressurechamber from the ink introducing mechanism.

Such a flat plate structure is formed by an anisotropic etching of aphotosensitive glass substrate. That is, the above-described substrateis the photosensitive glass substrate, and the nozzles, the ink slits,the pressure chambers and the ink introducing mechanism are formed bythe anisotropic etching of this substrate. In this manner, the etchingdepth can be exactly controlled, and thus the ink slits can be readilydeepened. Further, by using the process for exposing the substrate whilethe substrate is rotated and inclined in the anisotropic etching, thenozzle having a tapered internal shape can be readily formed.

In the present invention, further, the nozzles can be separated into aplurality of groups. Of course, the zig zag arrangement is applied toeach of the groups. By this method, groups of pressure chambers and inkslits corresponding to the groups of nozzles arranged in differentportions can be groups of ink paths separated from each other. In thisstructure, by supplying different colors of inks to the groups of inkpaths, color printing can be carried out. Also, the pressure variationin one group of ink path hardly affects the other ink paths. That is,the pressure variation can be decentralized. The number of the separatedarrangement groups, for example, can be preferably three.

In this flat plate structure, the piezoelectric elements can be used asthe above-described pressing elements. In the present invention, sincethe nozzle interval restriction is moderated by the zig zag arrangement,the depth of the ink paths can be shallowed in comparison with thethickness of the substrate. Hence, it becomes difficult for thevibration of one piezoelectric element to affect other parts of thehead.

By providing the piezoelectric elements as the pressing elements to thecorresponding pressure chambers, the ink can be selectively dischargedfrom the nozzles. At this time, the structure of the piezoelectricelements can be a single piezoelectric substrate. This piezoelectricsubstrate has a circular or a circular arc form, and is formed with acommon electrode on one surface and a plurality of individual electrodeson another surface corresponding to the pressure chambers. Hence, thepiezoelectric substrate, each individual electrode and the commonelectrode can constitute a single piezoelectric element. That is, on asingle piezoelectric substrate, a plurality of piezoelectric elementscan be formed for every individual electrode. In this manner, aplurality of Piezoelectric elements can be constructed as one component,and thus its production can be made easy.

When the plurality of piezoelectric elements are formed to a singlemember, further, by providing concave surfaces between the electrodes,the piezoelectric elements can be electrically and acousticallyinsulated from each other. This improves the printing quality.

Also, by arranging the piezoelectric substrate so that the individualelectrodes may face opposite sides of the pressure chambers, the wiringto the individual electrodes can be made easy. Also, by arranging thenozzles so that the nozzles may open to the opposite side of thepiezoelectric element mount surface of the substrate, the wiring to theindividual electrodes can be further readily carried out.

Further, by forming the opening of each nozzle to be substantially acircular form, occurrence of so-called satellite can be prevented toraise the printing quality.

As a typical example of the zig zag arrangement of the presentinvention, there is an inclined zig zag arrangement. This arrangement isa zig zag arrangement and further the first and second straight linesare inclined with respect to the printing direction and the directionperpendicular to the printing direction. In this arrangement, since thenozzle interval restriction can be further moderated, theabove-described advantages can be made more remarkable.

The present invention can be constructed as a head unit. This head unitcomprises:

a) an ink jet print head which includes:

a1) a plurality of nozzles arranged in a zig zag arrangement on a flatsurface for discharging ink; and

a2) discharge means for causing discharge of the ink from the nozzles;and

b) a support for supporting the ink jet print head.

Further, the present invention can be constructed as a non-impactprinter. This non-impact printer comprises:

a) a head unit which includes;

a1) an ink jet print head which includes:

a11) a plurality of nozzles arranged in a zig zag arrangement on a flatsurface for discharging ink; and

a12) discharge means for causing discharge of the ink from the nozzles;and

a2) a support for supporting the ink jet print head; and

b) an ink fountain for storing the ink to be discharged.

In these cases, the ink jet print head can be carried out in any of theabove-described embodiments. When the piezoelectric elements are used asthe discharge means, the head unit of the present invention is providedwith a member for connecting the piezoelectric elements to a signalvoltage source. Also, the non-impact printer of the present inventionincludes the signal voltage source for supplying the command as thesignal voltage to the piezoelectric elements.

The non-impact printer can be constructed to include the followingparts.

a) a platen for holding a printing medium;

b) a feed roller for feeding the printing medium to the platen along adirection perpendicular to the printing direction;

c) means for giving a feeding force to the feed roller;

d) a carriage movable to and from the platen in the printing direction;and

e) means for giving a driving force to the carriage,

f) wherein the head unit is relatively secured to the carriage, and withthe moving of the carriage, the head unit is movable with respect to theprinting medium in the printing direction, and wherein with the feedingof the printing medium by the feed roller, the head unit is movable withrespect to the printing medium in a direction perpendicular to theprinting direction.

In this apparatus of the present invention, in particular, the apparatushaving the nozzles arranged in the inclined zig zag arrangement, theproblem caused is that preprocessing such as an order operation and thelike is previously applied to data to be used when the nozzles aredriven. The third object of the present invention is to solve thisproblem to improve the usability. That is, the object is to provide adriving method practicable in an ink jet print head driver circuit sideand an ink jet print head driver circuit for carrying out this drivingmethod. Further, by describing this object in other words, the object isto provide an ink jet print head driver circuit provided with hardwarecapable of performing this preprocessing.

The driving method and the driver circuit of the present invention drivethe nozzles arranged in the inclined zig zag arrangement, and theinclined zig zag arrangement satisfies the above-described threeconditions. Now, in order to explain the driving method and the drivercircuit of the present invention, the following terms are defined.

a) Odd numbers are assigned in order to the nozzles arranged on thefirst straight line. That is, the nozzles positioned in the odd numberorders along the direction perpendicular to the printing directionwithin the plurality of nozzles are arranged on the first straight line;and

b) Even numbers are assigned in order to the nozzles arranged on thesecond straight line. That is, the nozzles positioned in the even numberorders along the direction perpendicular to the printing directionwithin the plurality of nozzles are arranged on the second straightline.

The driving method of the present invention comprises the followingsteps.

a) a first step for separating the input serial data into odd-side dataand even-side data;

b) a second step for delaying the odd-side data a first predeterminedtime when the first straight line is positioned ahead of the printingdirection and the even-side data the first predetermined time when thesecond straight line is positioned ahead of the printing direction; thefirst predetermined time corresponding to a printing direction intervalbetween the nozzles being arranged adjacent to each other along thedirection perpendicular to the printing direction;

c) a third step for delaying the odd-side data and the even-side data asecond predetermined time; when the first straight line is positionedahead of the printing direction, a delay target in the third step beingthe odd-side data delayed in the second step and the even-side dataseparated in the first step; when the second straight line is positionedahead of the printing direction, a delay target in the third step beingthe odd-side data separated in the first step and the even-side datadelayed in the second step; the second predetermined time beingproportional to a product of the printing direction interval between thetwo nozzles arranged adjacent to each other on the same straight lineand the position along the direction perpendicular to the printingdirection of the nozzle arranged adjacent to each other on the samestraight line; an order of the second predetermined time against thedata to be delayed being changed depending on the printing direction sothat the second predetermined time of the nozzles positioned ahead ofthe printing direction is relatively large and the second predeterminedtime of the nozzles positioned behind of the printing direction isrelatively small;

d) a fourth step for carrying out a serial/parallel conversion of theodd-side and even-side data delayed in the third step to obtainodd-nozzle parallel data and even-nozzle parallel data; the odd nozzleparallel data and the even-nozzle parallel data having bit arrangementscorresponding to the positions of the nozzles on the first and secondstraight lines along the direction perpendicular to the printingdirection, respectively; and

e) a fifth step for selectively discharging the ink from the nozzles bydriving the discharging means on the basis of the odd-nozzle paralleldata and the even-nozzle parallel data; the driving executing so thatthe ink being discharged from the nozzles located in positionscorresponding to the bits of the odd-nozzle parallel data and theeven-nozzle parallel have a predetermined data value and the ink notbeing discharged from the nozzles located in positions corresponding tothe bits not having the predetermined value.

Also, the driver circuit of the present invention comprises thefollowing:

a) odd-even separating means for carrying out the first step;

b) delay means for adapting the data order to the offset along theprinting direction, thus carrying out the second step;

c) delay means for adapting the data order to the offset in inclinedarrangement by carrying out the third step;

d) serial/parallel converting means for carrying out the fourth step;and

e) driving means for carrying out the fifth step.

The present invention can be also expressed as a preprocessing circuitcorresponding to a preprocessing part of the above-described drivercircuit. This preprocessing circuit comprises the following:

a) odd-even separating means for carrying out the first step;

b) delay means for adapting the data order to the offset along theprinting direction, thus carrying out the second step; and

c) delay means for adapting the data order to the offset in inclinedarrangement, thus carrying out the third step.

In the driving method and the driver circuit of the present invention,first, the input serial data are separated into odd-side data andeven-side data. By this odd-even separation processing, the input serialdata are divided into two groups. Then, depending on the positions ofthe nozzles and the printing direction, the delay processing of thegroups of data is executed.

It is necessary to consider the positions of the nozzles in the inclinedzig zag arrangement by separating the following two components. First isthe positional relationship between the first and second straight lines.The data for driving the nozzles on one straight line which are ahead ofthe printing direction must be older data, for the time corresponding tothe printing direction interval between the two straight lines, than thedata for driving the nozzles on another straight line which are behindthe printing direction.

Second is the mutual positional relationship between the nozzlesarranged on the same straight line. In the inclined zig zag arrangement,since the two straight lines are inclined against the printingdirection, the positions along the printing direction of the nozzles onthe same straight line are different. The data for driving one nozzle atone position along the printing direction must be older data for thetime corresponding to the printing direction interval between thenozzles adjacent on same straight line, than the data for drivinganother nozzle at the next position along the printing direction.

Further attention should be paid to the fact that such positionalrelationships depend on the printing direction.

In the present invention, the second step is executed in order to adaptthe first relation. In this step, the odd-side data and the even-sidedata obtained in the first step are selectively delayed thepredetermined amounts. According to the aforementioned definition of theterms, the nozzle arranged on the first straight line is given the oddnumber, and the nozzle arranged on the second straight line is given theeven number. The target data for the delay in the second step are thedata corresponding to this number. That is, when the first straight lineis positioned ahead of the printing direction, the odd-side data aredelayed, and when the second straight line is positioned ahead of theprinting direction, the even-side data are delayed. At this time, thedelay time is set depending on the adaptability of the data with thefirst relation. That is, the delay time at this time is the timeequivalent to the interval along the printing direction between theadjacent nozzles along the direction perpendicular to the printingdirection.

By executing the second step of such contents, the first relationconcerning the positions of the nozzles can be satisfied on the dataside in consideration of the printing direction. First, when the firststraight line is positioned ahead of the printing direction, theodd-side data for use in driving the nozzles arranged on the firststraight line are delayed. As a result, when it is observed at a certaintiming, the odd-side data become the old data compared with theeven-side data for use in driving the nozzles arranged on the secondstraight line. On the other hand, when the second straight line ispositioned ahead of the printing direction, the even-side data fordriving the nozzles arranged on the second straight line are delayed. Asa result, when it is observed at a certain timing, the even-side databecome the old data compared with odd-side data for use in driving thenozzles arranged on the first straight line. The time difference betweenboth, in any case, becomes the time equivalent to the interval along theprinting direction between the adjacent nozzles along the directionperpendicular to the printing direction.

Then, the third step is executed for adapting the second relation. Inthis step, the odd-side data obtained in the first step, the even-sidedata obtained in the first step, the odd-side data delayed in the secondstep and the even-side data delayed in the second step are selectivelydelayed.

First, when the first straight line is positioned ahead of the printingdirection, the odd-side data delayed in the second step and theeven-side data separated in the first step become the target for delayin this step. As described above, the odd-side data and the even-sidedata correspond to the first and second straight lines, respectively. Onthe other hand, when the first straight line is positioned ahead of theprinting direction, in order to drive the nozzles present on the firststraight line, the older data than the data used for driving the nozzleson the second straight line must be used. Hence, in this step, theodd-side data delayed on the second step and the even-side dataseparated in the first step are delayed for driving nozzles on the firstand second straight line, respectively.

Next, when the second straight line is positioned ahead of the printingdirection, the odd-side data separated in the first step and theeven-side data delayed in the second step are the target for the delayin this step. When the second straight line is positioned ahead of theprinting direction, in order to drive the nozzles present on the secondstraight line, the older data than the data used for driving the nozzleson the first straight line must be used. Hence, the odd-side dataseparated in the first step and the even-side data delayed in the secondstep are delayed for driving nozzles on the first and second straightline, respectively.

The delay time in the third step is different for every nozzle. This isthe reason why the second relation to be adapted in this step is thepositional relation of the nozzles arranged on the same first or secondstraight line. In the setting of the delay time in this step, thepositions of the nozzles on each straight line must therefore beconsidered. More specifically, the delay time in this step becomes thetime proportional to the product of the interval along the printingdirection of the adjacent two nozzles on the same straight line and theposition along the direction perpendicular to the printing direction ofeach nozzle on the same straight line. Also, it is necessary todetermine the setting of the delay time depending on the printingdirection. That is, the order of the delay time of the data to be thetarget for the delay is changed depending on the printing direction soas to be relatively large for the nozzle positioned ahead of theprinting direction and to be relatively small for the nozzle positionedbehind the printing direction.

As described above, the two groups of the date adapted for the first andsecond relations are used for the driving of the corresponding nozzles.That is, in the fourth step, the serial/parallel conversion of thesedata is executed, and in the fifth step, the parallel data obtained inthe fourth step are actually used for the discharge control of the ink.

In more detail, in the fourth step, the serial/parallel conversion ofthe odd-side data delayed in the third step is carried out to obtain theodd-side parallel data. This odd-side parallel data have the bitarrangement corresponding to the position of the nozzle along thedirection perpendicular to the printing direction on the first straightline. In the fifth step, based on the odd-side parallel data, thedischarge means is driven, and the ink is selectively discharged fromthe plurality of nozzles. In this case, the discharge is executed, forexample, the bits corresponding to the nozzles have the predeterminedvalue such as "1".

Similarly, in the fourth step, the serial/parallel conversion of theeven-side data delayed in the third step is carried out to obtain theeven-side parallel data. This even-side parallel data have the bitarrangement corresponding to the position of the nozzle along thedirection perpendicular to the printing direction on the second straightline. In the fifth step, based on the even-side parallel data, thedischarge means is driven, and the ink is selectively discharged fromthe plurality of nozzles.

By these driving method or the driver circuit, there is no need topreviously apply preprocessing to the input serial data, and thus theusability is extremely improved. Also, by implementing the circuit as anIC or LSI, the circuit structure of the ink jet printer can besimplified. Also, it is possible to construct the circuit executing thesecond to fifth steps by the odd and even systems of unit circuits, andhence the circuit construction can be produced into units and thus canbe simplified.

Further, the printing direction can be detected by a printing directionsignal. That is, it is sufficient to switch the operations of the secondand third steps by using the printing direction signal exhibiting theprinting direction. More specifically, the selection of the targets forthe delay and the setting of the delay time can be executed depending onthe value of the printing direction signal.

Also, the odd-even separation can be executed by using two-phase clocks.That is, prior to the first step, the odd-side and even-side clocks ofmutually opposite phases are generated. This two-phase clock generationoperation is realized by dividing the clock synchronized with the inputserial data.

When the two-phase clocks are used in the odd-even separation, in thefirst step, by latching the input serial data depending on the odd-sideclock, the odd-side data are obtained, and by latching the input serialdata depending on the even-side clock, the even-side data are obtained.

In the second step, first, when the first straight line is positionedahead of the printing direction, the odd-side clock is selected as thefirst clock for delay, and when the second straight line is positionedahead of the printing direction, the even-side clock is selected as thefirst clock for delay. Then, the input serial data are latched dependingon the first clock for delay and the predetermined amount of bit shiftof the data is carried out to execute the delay of the first relation.

In the third step, first, the serial/parallel conversion of the odd-sidedata and the even-side data is carried out depending of the respectiveodd-side and even-side clocks. Next, the odd-slide data and theeven-side data obtained in the serial/parallel conversion are delayedfor every bit so as to adapt for t;he second relation. Further, the bitsof the delayed odd-slide and even-side data are multiplexed,respectively, to perform the parallel/serial conversion. At this time,the multiplexing directions are switched depending of the printingdirection so that the bit order of the odd-side data or, the even-sidedata before the serial/parallel conversion depending on the odd-sideclock or the even-side clock may be restored.

Next, in the fourth step, the serial/parallel conversion of the odd-sidedata and the even-side data delayed in the third step is carried outdepending on the odd-side clock and the even-side clock to obtain theodd-nozzle parallel data and the even-nozzle parallel data.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention willbecome more apparent from the consideration of the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a top view of a first embodiment of an ink jet print headaccording to the present invention;

FIG. 2 is a top view showing an arrangement of piezoelectric elementsshown in FIG. 1;

FIG. 3 is an enlarged top view showing a construction near nozzles shownin FIG. 1;

FIG. 4 is a top view of a second embodiment of an ink jet print headaccording to the present invention;

FIG. 5 is a top view showing a piezoelectric substrate of a thirdembodiment of an ink jet print head according to the present invention;

FIG. 6 is a top view showing a piezoelectric substrate of a fourthembodiment of an ink jet print head according to the present invention;

FIG. 7 is a top view of a fifth embodiment of an ink jet print headaccording to the present invention;

FIG. 8 is an enlarged top view showing a construction near nozzles shownin FIG. 7;

FIG. 9 is a cross sectional view, taken along the line B--B shown inFIG. 8;

FIG. 10 is a longitudinal cross sectional view of the ink jet print headshown in FIG. 7, mounted on a support;

FIG. 11 is a schematic view showing a basic principle of a Kyserpiezoelectric head unit;

FIG. 12 is a top view of a sixth embodiment of an ink jet print headaccording to the present invention;

FIG. 13 is an enlarged top view showing a construction near nozzlesshown in FIG. 12;

FIG. 14 is a cross sectional view, taken along the line A--A shown inFIG. 13;

FIG. 15 is a schematic view showing one example of a dimension ratiodetermination in the ink jet print head shown in FIG. 12;

FIG. 16 is a cross sectional view of a nozzle of a seventh embodiment ofan ink jet print head according to the present invention;

FIG. 17 is a top view of an eighth embodiment of an ink jet print headaccording to the present invention;

FIG. 18 is a top view of an essential part of a ninth embodiment of anink jet printer according to the present invention;

FIG. 19 is an elevational view of an essential part of the ink jetprinter shown in FIG. 18;

FIG. 20 is a side view of an essential part of the ink jet printer shownin FIG. 18;

FIG. 21 is a schematic view showing an inclined zig zag arrangement in atenth embodiment of an ink jet print head according to the presentinvention;

FIG. 22 is a block diagram of a driver circuit of the tenth embodimentof the ink jet print head according to the present invention;

FIG. 23 is a block diagram of a clock generator shown in FIG. 22;

FIG. 24 is a block diagram of an odd-even separator shown in FIG. 22;

FIG. 25 is a timing chart showing an operation of the clock generatorand the odd-even separator shown in FIG. 22;

FIG. 26 is a block diagram of an odd-side delay & multiplexer (MUX)shown in FIG. 22;

FIG. 27 is a block diagram of an even-side delay & multiplexer shown inFIG. 22;

FIG. 28 is a schematic view showing an operation of the odd-side delay &multiplexer and the even-side delay & multiplexer shown in FIG. 22;

FIG. 29 is a block diagram of an odd-side output circuit shown in FIG.22;

FIG. 30 is a block diagram of an even-side output circuit shown in FIG.22;

FIG. 31 is a circuit diagram of shift registers shown in FIGS. 26 and27;

FIG. 32 is a top view, partly in section, of a conventional ink jetprint head;

FIG. 33 is a top view of an ink jet print head having nozzles arrangedalong a vertical line;

FIG. 34 is top view showing a dot pattern obtained by printing by usingthe head shown in FIG. 33; and

FIG. 35 is a block diagram of a conventional driver circuit for athermal printer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in connection with itspreferred embodiments with reference to the accompanying drawings,wherein like reference characters designate like or corresponding partsthroughout the views and thus the repeated description thereof can beomitted for brevity.

Modification of the prior art

Before explaining embodiments of the present invention, an improvementof an arrangement of nozzles of an ink jet print head made by inventorsof the present invention will now be described in connection with FIG.33 and FIG. 34.

For example, an arrangement of nozzles 18 of an ink jet print headcapable of improving problems of the prior art described above is shownin FIG. 33. In this case, the nozzles 18 are arranged along a straightline. In the conventional rhombic arrangement of the nozzles 18 shown inFIG. 32, paying attention to one side of the rhombic form, the ink slits16 for supplying the ink to the nozzles 18 arranged on this side are allpresent on the same side. On the contrary, in the straight linearrangement of the nozzles shown in FIG. 33, the ink slits 16 forsupplying the ink to the nozzles 18 are alternately present on both theleft and right sides of the straight line. For example, in FIG. 33, theink slit 16 of the uppermost nozzle 18 is arranged on the left side, andthe ink slit 16 of the next nozzle 18 is on the right side. The ink slit16 of the next nozzle 18 is on the left side, and the ink slit 16 of thelowermost nozzle 18 is on the right side. That is, the ink slits 16 ofthe nozzles 18 are alternately arranged on both the left and right sidesof the straight line. In this case, the nozzles 18 are arranged on thestraight line and the ink slits 16 of the nozzles 18 are alternatelydrawn out of the nozzles 18 from the left and right sides. As a result,compared with the prior art shown in FIG. 32, the interval between thenozzles 18 can be reduced and thus the dot interval can be diminished.

When the printing is cart led out by using the head having the nozzles18 arranged as described above, the head is moved in the directionperpendicular to the arranging direction of the nozzles 18, as indicatedby an arrow shown in FIG. 33. By discharging the ink at the same timefrom the nozzles 18 while the head is moved in such a direction, asshown in FIG. 34, one straight line is formed by dots 24. Since one lineis obtained per one discharge, by repeating a discharge control at apredetermined timing, a plurality lines can be successively printed.

Driver circuit for thermal printer

When such a driving of the head is carried out, a driver circuit for athermal printer conventionally known can be used. In FIG. 35, there isshown a driver circuit for a thermal printer.

The driver circuit is a circuit for performing a printing of 48 dots perone line and includes a shift register 25, a latch 26 and a plurality(48) of ANDs 28. The shift register 25 converts input serial data into48 bits of parallel data at a clock timing. That is, the shift register25 acts as a serial/parallel (S/P) converter of 48 bits. The latch 26latches the parallel data output from the shift register 25 according toa latch signal supplied from an external device such as a CPU for aprint control.

The data latched in the latch 26 are supplied as drive signals to thehead of the thermal printer, that is, heating elements constituting thethermal head, more specifically, to bases (gates) of transistor s fordriving the heating elements. In other words, when one bit of datarepresents one predetermined value such as "1" and another bit of datarepresents another predetermined value such as "0" in the latch 26, theheating element corresponding to one bit of data is heated and theheating element corresponding to another bit of data is not heated.

In this case, the heating period is controlled by a strobe signal. Thatis, the 48 ANDs 28 corresponding to 48 bits in the latch 26 input thedata from the latch 26 and also input the strobe signal from theexternal device. Hence, the aforementioned heating operation is carriedout in only the on-period of the strobe signal. That is, the strobesignal is used for controlling the printing density of the dots. In thiscase, OUT1 to OUT48 are outputs to be supplied to the transistors fordriving the heating elements of the bits.

The above-described construction can be applicable to the ink jet printhead driver circuit. However, in the ink jet printer, the outputfunction is borne by not the heating elements of the thermal printer butthe plezo-electric elements (see FIG. 32). Hence, in order to apply thecircuit shown in FIG. 35 to the ink jet print head driver circuit, it isnecessary to modify the circuit bearing the output function. Morespecifically, the outputs OUT1 to OUT48 are required to be supplied tonot the circuit for controlling the power supply to the heating elementsbut a push-pull driver circuit capable of performing the charge anddischarge of the piezoelectric elements.

On the other hand, recently, higher definition printing has beenrequired, and thus the shortening of the dot interval is beinginvestigated. In the ink jet print head shown in FIG. 33, the intervalbetween the dots 24 is basically decided by the internal between thenozzles 18 or the interval between the ink slits 16. In turn, since theinterval between the nozzles 18 or the ink slits 16 connected thereto isdetermined by their processing steps, it can be considered that there isa limit due to the processing for obtaining the higher definitionprinting by the reduction of the interval between the dots 24.

The embodiments of the present invention

The embodiments hereinafter described are constructed from the viewpointof the reduction of the interval between the dots 24. From the followingdescription, it will become more apparent for those skilled in the artthat this object can be properly achieved and various changes andmodifications in the embodiments can be made. Further, it will becomeapparent that the embodiments are not obtained by a simple combinationof the structures shown in FIGS. 32 to 35.

The first embodiment

In FIGS. 1 to 3, there is shown the first embodiment of an ink jet printhead according to the present invention. As shown in these drawings,this embodiment is characterized by a zig zag arrangement of the nozzles18.

As shown in FIG. 1, an ink chamber 12 is formed as a circle, andpressure chambers 14 for receiving the ink from the ink chamber 12 andstoring the ink therein are arranged around the circle inside the inkchamber 12. The pressure chambers 14 are connected to respective inkslits 16, and the ink slits 16 lead the ink to the respective nozzles 18from the respective pressure chambers 14. The nozzles 18 are locatednear the center of the circle.

The ink chamber 12, the pressure chambers 14, the ink slits 16, thenozzles 18 and the like are formed on a rectangular substrate 40 byetching. Also, an ink introducing aperture 42 for introducing the ink tothe ink chamber 12 is formed in one corner of the substrate 40 byetching.

As shown in FIG. 2, in this embodiment, a plurality of piezoelectricelements 30 are arranged in an annular shape. The piezoelectric elements30 corresponding to the pressure chambers 14 shown in FIG. 1 areattached to the respective pressure chambers 14 in the arrangement shownin FIG. 2. Hence, in this case, since each piezoelectric element 30 isprovided to each pressure chamber 14, the ink discharge from respectivenozzles 18 can be controlled independently of each other.

As shown in FIG. 3, the nozzles 18 have substantially a circular form.Hence, a form of an ink drop discharged from the nozzle 18 becomessubstantially a circular form, and a stable printing without satellitecan be carried out. The half of the nozzles 18 supplied with the inkfrom the left hand side in the figure are arranged along one verticalline, and the other half of the nozzles 18 supplied with the ink fromthe right hand side are arranged along another vertical line. Also, thenozzles 18 arranged on the left hand side line are offset by the halfinterval with respect to the nozzles 18 arranged on the right hand sideline. This arrangement of the nozzles 18 is hereinafter referred to as azig zag arrangement.

When the printing is executed in this embodiment, a voltage isselectively applied to the piezoelectric elements 30 so as toselectively excite the same. Then, the ink is caused to flow into thepressure chambers 14 corresponding to the excited piezoelectric elements30 from the ink chamber 12, and the ink flows out from the pressurechambers 14 to the nozzles 18 via the ink slits 16. When the excitationof the piezoelectric element 30 is released, almost the same amount ofink is introduced into the corresponding pressure chamber 14.

In this embodiment, since the interval between the nozzles 18 arrangedin the vertical direction is substantially shortened due to the zig zagarrangement of the nozzles 18, the printing can be carried out so as toperform relatively high dot density.

Further, since the nozzles 18 possess a substantially circular form, theform of the ink drop discharged from the nozzles 18 is substantiallycircular, and thus the printing becomes stable. For the same reason, anoccurrence of a so-called satellite can be prevented.

Also, the flat surface structure in this embodiment can be formed byanisotropic etching of a photosensitive glass substrate. That is,although conventionally a substrate capable of being subjected to onlyisotropic etching is used, by using the photosensitive glass substrateadaptable to the anisotropic etching, the depth of the ink chamber 12and the ink slits 16 can be readily controlled in the production of theink jet print head. As a result, compared with the conventional ink jetprint head, in particular, in the ink slits 16, the depth of the partnear the nozzles 18 can be increased. When the depth of the ink slits 16is enlarged, the width of the ink slits 16 near the nozzles 18 can bethinned. That is, by increasing the depth of the ink slits 16, in spiteof reducing the width, the cross section can be enlarged. Hence, theinterval between the ink slits 16 can be reduced without increasing theviscous drag, and thus the interval between the nozzles 18 can bereduced. Also, the production process can be simplified.

In addition, since the pressure chambers 14 are arranged in a circle,similar to the conventional embodiment, the length of the ink slits 16can be almost equal to realize the equalization of the viscous drag.Also, since the pressure chambers 14 are provided in the radial form,the number of nozzles 18 per unit area can be enlarged.

Further, it is readily understood for those skilled in the art that,even when the pressure chambers 14 are arranged in a circular are, thesame effects can be obtained. Of course, this is the same in thefollowing embodiments.

The second embodiment

In FIG. 4, there is shown the second embodiment of an ink jet print headaccording to the present invention.

In this embodiment, the nozzles 18 are separately formed in three partsnear the central part of the circle, and the ink chamber 12 is separatedinto four ink chambers 12-1, 12-2, 12-3 and 12-4. First, to a firstgroup of nozzles 18 shown in the upper part in the figure, the ink issupplied from the first ink chamber 12-1. To the second group of nozzles18 shown in the middle part, the ink is supplied from the second andthird ink chambers 12-2 and 12-3. To the third group of nozzles 18 shownin the lower part, the ink is supplied from the fourth ink chamber 12-4.

Hence, in this embodiment, compared with the first embodiment, colorprinting can be carried out. More specifically, by supplying differentcolors (cyan, magenta and yellow) of inks to the first ink chamber 12-1,the second and third ink chambers 12-2 and 12-3 and the fourth inkchamber 12-4, color printing can be performed. Also, since the nozzles18 are provided in the zig zag arrangement, the multi-dot printing canbe carried out in the same manner as the first embodiment.

Further, in this embodiment, since the ink chambers 12-1, 12-2, 12-3 and12-4 are separated for every group of nozzles 18, the pressure variationcaused in one pressure chamber 14 with the ink discharge can not easilyaffect the nozzles 18 supplied with the ink from another ink chamber. Asa result, a relatively stable printing quality can be obtained.

Further, the nozzles 18 can be separated into four groups, and in thiscase, one more color ink such as black ink can be supplied. Of course,according to the present invention, the number of the nozzle separationgroups is not restricted.

The third embodiment

In FIG. 5, there is shown a piezoelectric substrate 32 in the thirdembodiment of an ink jet print head according to the present invention.

In this embodiment, as shown by an enlarged part in the left hand sidein FIG. 5, a plurality of electrodes 34 are separately formed on apiezoelectric substrate 32 at a predetermined interval. Also, a commonelectrode (not shown) is formed on the opposite surface of thepiezoelectric substrate 32 to the surface on which the electrodes 34 areformed. The other parts of the ink jet print head are the same as thoseof the first or second embodiment, and thus they are not shown and notdescribed for brevity.

In this embodiment, there is no need to attach a number of piezoelectricelements 30 on the substrate 40, which is different from the firstembodiment. Also, since the piezoelectric substrate 32 has an annularform, the interval between the electrodes 34 can be designed to berelatively large, and thus interference between the electrodes 34 isless likely to be caused. In this case, the piezoelectric substrate 32can be arranged so that the side of the electrodes 34 or the commonelectrode may face the pressure chambers 14. Both ways are possible.When the common electrode side of the piezoelectric substrate 32 isattached to face the pressure chamber side, the wiring to connect theelectrodes 34 can be readily carried out.

The fourth embodiment

In FIG. 6, there is shown a piezoelectric substrate 36 in the fourthembodiment of an ink jet print head according to the present invention.

In this embodiment, the piezoelectric substrate 36 has the sameconstruction as the piezoelectric substrate 32 in the third embodimentshown in FIG. 5, except that notches or grooves 38 are formed betweenthe electrodes 34 on the piezoelectric substrate 36. Accordingly, theelectrodes 34 can be electrically and acoustically insulated orseparated from each other. Hence, the interference between theelectrodes 34 can be reduced considerably, and printing with highaccuracy can be carried out.

The fifth embodiment

In FIG. 7, there is shown the fifth embodiment of an ink jet print headaccording to the present invention.

In this embodiment, in the substrate 40, the nozzles 18 are formed so asto penetrate in the thickness direction by etching. FIG. 8 shows anenlarged form near the nozzles 18, and FIG. 9 is an enlarged crosssection of the nozzle 18, taken along the line B--B in FIG. 8. In thiscase, the hole of the nozzles 18 is tapered off at an angle ofapproximately 2°.

As shown in FIG. 10, a diaphragm 46 and piezoelectric elements 30 aremounted on the substrate 40, and the substrate 40 is mounted on asupport 48. For example, the material of the diaphragm 46 is glass. Thediaphragm 46 is mounted on the substrate 40 by using screws, an adhesiveor the like so as to cover the pressure chambers 14, the ink slits 16and the ink introducing aperture 42. At this time, the piezoelectricelements 30 are attached onto the diaphragm 46 in the positionscorresponding to the pressure chambers 14. To each piezoelectric element30, a flexible cable 50 is connected. The flexible cable 50 acts toapply a signal voltage output from a signal source (not shown) to eachpiezoelectric element 30.

The support 48 is composed of a material having a high rigidity such asa metal, a high rigidity resin or the like. On the support 48, thesubstrate 40 is mounted. In the support 48, hollows 52 are formed in thesurface supporting the substrate 40 in the portions corresponding to thepiezoelectric elements 30. In FIG. 10, the adhesive is filled up inportions 54 so as to fix the substrate 40 on the support 48.

Now, when the voltage is applied to one piezoelectric element 30 fromthe signal source via the flexible cable 50, the corresponding part ofthe diaphragm 46 is stressed by the piezoelectric function of thepiezoelectric element 30, and the volume in the corresponding pressurechamber 14 is changed. Thus, the ink is discharged from thecorresponding nozzle 18. In this embodiment, since the diaphragm 46 issupported by a projection 48a of the support 48, only the partcorresponding to the excited piezoelectric element 30 in the diaphragm46 is deformed, but the parts corresponding to the adjacentpiezoelectric elements 30 to the excited piezoelectric element 30 arenot unnecessarily bent. After the ink discharging operation, thediaphragm 46 is returned to the original state. Since the negativepressure is generated in the corresponding pressure chamber 14 by thismotion, the same amount of ink as the discharged amount is supplied tothe corresponding pressure chamber 14 via the ink introducing aperture42 and the ink chamber 12.

As described above, in this embodiment, the head structure of the firstembodiment is described along with its support means. Hence, the headstructure itself is not restricted to that of the first embodiment, andthus the head structures of the second to fourth embodiments can beused. Of course, the basic concept of the present invention is notrestricted to only the first to fourth embodiments.

The construction of the fifth embodiment, as described hereinafter inconnection with FIG. 11, can be applied to a non-impact printer.Accordingly, compared with a conventional printer, a non-impact printerwith an improved printing quality and high performance can beimplemented.

In FIG. 11, there is shown a non-impact printer, in particular, a basicconstruction of its head unit. This head unit uses the so-called Kyserpiezoelectric head unit as the basic principle.

The ink jet printers are roughly classified into two types such as acontinuous type and an on-demand type. In the former, the ink iscontinuously ejected from the nozzle and the unnecessary ink for theprinting is collected for reuse. Hence, since a head response is highbut a mechanism for collecting the ink is required, the apparatus iscomplicated and expensive. In turn, in the latter, since the ink ejectis executed only when it is required, the head response is low but theapparatus is simple and inexpensive.

The on-demand type includes an electrostatic attraction (deflection)type for drawing the ink from the nozzle by the electro-static force anda pressure pulse type for pushing out the ink from the nozzle byapplying a pressure to the pressure chamber. Further, the pressure pulsetype includes a piezoelectric type and a bubble type. In thepiezoelectric type, the ink is pressurized by a piezoelectric element,and there are two types such as a one chamber type in which the ink issupplied from the respective pressure chambers to the correspondingnozzles and a two chamber type in which the ink is supplied from therespective pressure chambers to the corresponding temporary storingchambers. In the latter, the temporary storing chambers have a largediameter than the diameters of the inlet apertures of the correspondingnozzles. The temporary storing chambers act as absorbers of irregularpressure variations. Further, the one chamber type includes a Kyser typehaving a flat pressure chamber and a Zoltan type having a cylindricalpressure chambers. The two chamber type includes a Stemme type in whichthe ink is supplied to the temporary storing chambers near the nozzles.

Hence, in this embodiments, an ink jet printer is a relatively low headresponse type and is capable of performing high quality printing. Inthis case, as the ink, both water based and oil based inks can be used.

It is necessary to take into consideration that FIG. 11 shows not anactual structure of a head unit but its principle. For example, in FIG.11, though a nozzle 18 is open in a parallel direction against a surfaceof a substrate 40, when the structure shown in FIG. 10 is applied tothat shown in FIG. 11, it will be apparent that the nozzle 18 is open inthe perpendicular direction to the surface of the substrate 40. Also,the reason why a support 48 is not shown is only for simplicity of thedrawing. In FIG. 11, a signal source 56 applies a signal voltage to apiezo-electric element 30 attached on a diaphragm 46, and an inkfountain 58 supplies ink 60 to a pressure chamber 14 via an inkintroducing aperture 42 and an ink chamber 12. An ink drop 60a isdischarged toward a printing medium 55 such as paper a plastic sheet orthe like from the nozzle 18. A pipe 57 connects the ink fountain 58 withthe ink introducing aperture 42, and the ink 60 is caused to flow withinthe pipe 57 by a capillary tube force to be led to the ink introducingaperture 42.

The sixth embodiment

In FIG. 12, there is shown the sixth embodiment of an ink jet print headaccording to the present invention. FIG. 13 shows an enlarged form nearthe nozzles 18.

In this embodiment, as shown in FIG. 13, the nozzles 18 are provided inthe zig zag arrangement. However, as will be apparent from the comparingof FIG. 12 with FIG. 1 or the like, two straight lines for the zig zagarrangement are given with a certain angle with respect to those shownin FIG. 1. In other words, in FIG. 1, the straight lines are arrangedperpendicular to the printing direction, but in FIG. 12, the straightlines are arranged not perpendicular to the printing direction butdiagonally across at the certain angle. This arrangement is hereinafterreferred to as an inclined zig zag arrangement.

As described above, in this embodiment, since the nozzles 18 areprovided in the inclined zig zag arrangement, the interval between thenozzles 18 can be further widened. As a result, the interval between thedots 24 can be narrowed to realize the high printing quality. Thiseffect is more remarkable compared with the first to fourth embodiments.Of course, the other effects obtained in the first embodiment can bealso obtained in this embodiment.

For example, as shown in FIG. 15, assuming that the inclination of thetwo straight lines for the inclined zig zag arrangement of the nozzles18 with respect to the printing direction (head moving direction) is1/2, the interval between the two nozzles 18 arranged on the samestraight line in the printing direction (left and right hand sidedirection in FIG. 12) becomes twice the interval of these two nozzles 18in the dot arrangement direction and down direction in FIG. 12). Hence,the interval between these two nozzles 18 in the print direction becomes5^(1/2) {=(1² +2²)^(1/2) } times of that in the dot arrangementdirection. When the printing is carried out at the density of 360 dotper inch by using the head with such a dimension ratio determination ofthe sixth embodiment, the interval of the two nozzles 18 arranged on thesame straight line becomes as follows:

1 (inch)/360 (dots)×2 (nozzles)×5^(1/2) =315 (μm) Thus, even when it isassumed that 50 μm is required for a wall thickness for partitioning thetwo ink slits 16, the width of each ink slit 16 can be sufficientlywide, for example, 265 μm. In the case of the first embodiment, with thesame dimension setting, it is 91 μm. Hence, when the sixth embodimentand the first embodiment are compared with each other in this dimensionSetting, the effect of the dot density improvement in the sixthembodiment is approximately three times that in the first embodiment.

As shown in FIG. 14, the nozzles 18 are formed so that the hole may betapered off at an inclination angle of more than 4°. In order to formthe nozzles 18 having such a form by anisotropic etching, for instance,it is sufficient to use the following process. That is, first, a patternmask is mounted on the surface of a photosensitive glass substrate, andthen this photosensitive glass substrate is secured on a work table.Next, the work table is rotated around a predetermined rotary axis. Atthis time, the work table is inclined at a predetermined angle at thesame time. In the state that the work table is rotated and inclined inthis manner, the surface of the photosensitive glass substrate,particularly, the portions for forming the nozzles 18 are exposed by anexposure optical system (not shown). Thus, the exposing amount in theperiphery of these portions is changed with the passage of time. Sincethe etching amount of the photosensitive glass substrate is changeddepending on the exposure amount, by applying the etching treatment, thenozzles 18 having the tapered form can be formed. By using this method,for example, the nozzles having the tapered form of an inlet dimension(di)/an outlet dimension (do)≧2.5 can be obtained.

When the nozzles 18 with the structure and the dimension as shown inFIG. 14 are designed, since the viscous drag of the ink 60 flowing tothe nozzle 18 is reduced, the driving voltage applied to thepiezoelectric elements 30 can be lowered and high speed printing can becarried out. This is achieved by the fact that the oscillation of thepiezoelectric elements 30 can be damped more quickly.

In general, the viscous drag R can be calculated as follows

    R (N·s/m.sup.5)=2·p·L·U.sup.2 /S.sup.3

wherein p: viscosity of ink 60 (N·s/m⁵)

L: length of path of ink 60 (m)

U: peripheral length of cross section of path of ink 60 (m)

S: cross sectional area of path of ink 60 (m²)

When the viscous drag R of the ink 60 at the various portions iscalculated by using this formula, the following table is obtained. Inthis table, the calculated viscous drags R in the sixth embodiment arecompared with those in the first embodiment.

                  TABLE 1                                                         ______________________________________                                                   First embodiment                                                                         Sixth embodiment                                        ______________________________________                                        Pressure chamber to                                                                        3.2 × 10.sup.11                                                                      1.69 × 10.sup.11                              Nozzle       3.7 × 10.sup.12                                                                      2.39 × 10.sup.12                              Whole        4.0 ' 10.sup.12                                                                            2.56 × 10.sup.12                              ______________________________________                                    

As is apparent from Table 1, in this embodiment, the viscous drag R isremarkably reduced to approximately 1/2. In this case, as p and L,typical values are used, and as U and S, the values used in comparingthe width of the ink slit 16 are used.

Also, as to the substrate for the head, one having a thickness of 0.5 mmor 1.0 mm has been heretofore used as standard. When the substrate 40having this thickness is used in the first or fifth embodiment, assumingthat the depth of the ink slits 16 is determined to, for example, 0.1mm, the depth of the nozzles 18 is 0.4 mm or 0.9 mm. Since a largeviscous drag R is given at the discharging time of the ink 60, inparticular, the thickness of the substrate 40 must be thinned. This hasbeen heretofore used as the reduction method of the viscous drag R. Inthis embodiment, the viscous drag R can be reduced without using thismethod. Hence, even when the dot density is increased, it is unnecessaryto reduce the thickness of the substrate 40, and as a result, it becomesunlikely that the vibration of one piezoelectric element 30 will affectother piezoelectric elements. From this viewpoint, the high speedprinting with high accuracy can be carried out.

Further, similar to the first to fourth embodiments, in this embodiment,the mounting structure of the fifth embodiment can be combined. Also, inthis embodiment, the piezoelectric elements 30 described in the first,third or fourth embodiment can be used, and thus the detaileddescription thereof can be omitted for brevity. Further, in the samemanner as the second embodiment, the nozzles 18 can be separated into aplurality of groups. When this embodiment is combined with the otherembodiments, of course, the effects of the other embodiments can beobtained.

The seventh embodiment

In FIG. 16, there is shown a cross section of a nozzle 18 of the seventhembodiment of an ink jet print head according to the present invention.The other parts of the ink jet print head can be the same as those ofthe first to sixth embodiments.

In this embodiment, as shown in FIG. 16, the form of the bore of thenozzle 44 is different from that in the sixth embodiment. That is, theinternal diameter of the bore of the nozzle 44 is stepwise changed. Inthis case, for example, the outlet dimension do of the nozzle 44 isdetermined to at least 1/3 of the inlet dimension di.

In this embodiment, the same effects as those of the sixth embodimentcan be obtained. The viscous drag R is calculated in the same manner asthe sixth embodiment, and the results are shown in the following table.As is apparent from this table, the reduction effect of the viscous dragR is more remarkable than the sixth embodiment, and the viscous drag Rcan be reduced to approximately 1/3 of the first embodiment.

                  TABLE 2                                                         ______________________________________                                                   First embodiment                                                                         Seventh embodiment                                      ______________________________________                                        Presure chamber to                                                                         3.2 × 10.sup.11                                                                      1.73 × 10.sup.11                              nozzle                                                                        Nozzle       3.7 × 10.sup.12                                                                      1.19 × 10.sup.12                              Whole        4.0 × 10.sup.12                                                                      1.36 × 10.sup.12                              ______________________________________                                    

Further, similar to the first to fourth embodiments, in this embodiment,the mounting Structure of the fifth embodiment can be combined. Also, inthis embodiment, the piezoelectric elements 30 described in the first,third or fourth embodiment can be used, and thus the detaileddescription thereof can be omitted for brevity. Further, in the samemanner as the second embodiment, the nozzles 44 can be separated into aplurality of groups. When this embodiment is combined with the otherembodiments, of course, the effects of the other embodiments can be alsoobtained. In this embodiment, the effect of the dot density improvementto the same extent as the sixth embodiment can be obtained.

The eighth embodiment

In FIG. 17, there is shown the eighth embodiment of an ink jet printhead according to the present invention.

In this embodiment, compared with the seventh embodiment, the shapes ofthe pressure chambers 14 and the ink slits 16 are designed so that theviscous drags of the ink 60 flowing from the respective pressurechambers 14 to the respective nozzles 18 may be equal to each other.More specifically, for the nozzle 18 connected to the ink slit 16 havinga relatively short length, that is, the nozzle 18 positioned in the endpart of the inclined zig zag arrangement, the peripheral length of thisink slit 16 is determined to be relatively small, and for the nozzle 18connected to the ink slit 16 having a relatively long length, that is,the nozzle 18 positioned in the central part of the inclined zig zagarrangement, the peripheral length of this ink slit 16 is determined tobe relatively large. As a result, the ink slits 16 are somewhat inclinedwith respect to the straight lines on which the nozzles 18 are arranged.In this case, regardless of the positions of the inclined zig zagarrangement, the ink discharge properties of the nozzles 18 can bemutually equalized.

In this embodiment, the effects obtained in the seventh embodiment canalso be achieved. Also, similar to the first to fourth embodiments, inthis embodiment, the mounting structure of the fifth embodiment can becombined. Also, in this embodiment, the piezoelectric elements 30described in the first, third or fourth embodiment can be used, and thusthe detailed description thereof can be omitted for brevity. Further, inthe same manner as the second embodiment, the nozzles 18 can beseparated into a plurality of groups. When this embodiment is combinedwith the other embodiments, of course, the effects of the otherembodiments can also be obtained.

The ninth embodiment

In FIGS. 18 to 20, there is shown the ninth embodiment according to thepresent invention, that is, a whole structure of an ink jet printerconstructed by using the structures of the aforementioned embodiments.FIG. 18 is a top view, FIG. 19 is a front view, and FIG. 20 is a sideview.

First, a platen 62 is constructed as a flat platen so as to miniaturizeand thin the whole size and to obtain a shape and dimension adaptable toa facsimile, plotter, bar code printer or the like. A printing medium isfed to the platen 62 in a direction indicated by arrows C shown in FIG.20.

Further, in order to achieve a correct feeding of the printing medium,feed rollers 64 and 66 are provided at the front and rear sides of theplaten 62. The feed rollers 64 and 66 together with idle rollers 68 and70 facing the respective feed rollers 64 and 66 hold the printing mediumbetween the two rollers so as to move forward the same. A pair ofcarriage guides 72 and 74 are provided above the platen 62.

A carriage 76 is slidably mounted on the carriage guides 72 and 74 so asto move in a D-E direction. A driving system (not shown) including astepping motor or another driving means is connected to the carriage 76so as to move the carriage 76 to any position in the row direction withrespect to a recording medium. Hence, the carriage 76 can be moved inboth the directions along the D-E direction by this driving force.

The head of one of the first to eighth embodiments described above isbuilt in the carriage 76 so as to direct to the printing mediumintroduced on the platen 62. The ink fountain 58 for supplying the inkto the head is mounted below the platen 62. The ink fountain 58 and theink introducing aperture 42 of the head are coupled by, for example, aflexible pipe 57 (not shown).

Further, in order to prevent solidification of the ink 60 in the nozzles18 when the nozzles 18 are not used, a cleaning unit 78 is alsoprovided. When no printing is executed, the carriage 76 is retracted sothat the head may face to the cleaning unit 78.

A feed motor 80 gives the driving force for the movement of therecording paper and the cleaning unit 78. Also, a carriage motor 82 fordriving the carriage 76 is mounted. In FIGS. 18 to 20, driving forcetransmission mechanisms for coupling the feed motor 80 and the carriagemotor 82 with the objects to be driven are not shown, but anyconventional means can be properly used.

The tenth embodiment

In FIG. 21, there is shown an arrangement of nozzles used in the tenthembodiment of an ink jet print head according to the present invention.In this embodiment, as shown in FIG. 21, a head including an inclinedzig zag arrangement of the nozzles is used in the same manner as thesixth to eighth embodiments.

In this embodiment, as shown in FIG. 21, the nozzles 18 are arranged ontwo straight lines extending in a direction not perpendicular to thehead moving direction (printing direction) but intersecting the same ata predetermined angle, as shown by two broken lines in FIG. 21. Also,the nozzles 18 (with odd numbers) arranged on one straight line areoffset with respect to the nozzles 18 (with even numbers) arranged onanother straight line in the direction perpendicular to the printingdirection. In this embodiment, for example, the first nozzle 18 isoffset with respect to the second nozzle 18 by 8 dots in the printingdirection and by one dot in the direction perpendicular to the printingdirection. Also, the two adjacent nozzles 18 arranged on the samestraight line are separated from each other by 4 dots in the printingdirection and by 2 dots in the direction perpendicular to the printingdirection. Such an inclined zig zag arrangement makes the intervalbetween the nozzles 18 in the direction perpendicular to the printingdirection narrow and enables the higher definition printing.

When the head of the inclined zig zag arrangement is driven, it is notenough to simply apply the driver circuit of the thermal head, asdescribed above, that is, to change only the output parts.

More specifically, in FIG. 35, prior to inputting into a shift register25, it is necessary to properly apply preprocessing to the serial data.For example, it is assumed that the outputs OUT1 to OUT48 shown in FIG.35 are allocated to the nozzles 18 with numbers 1 to 48 in FIG. 21. Inthis case, the data to be used for driving the nozzles 18 arranged onone straight line of the front in the printing direction must be delayedby 8 lines with respect to the data to be used for printing by thenozzles 18 arranged on another straight line of the rear in the printingdirection. Also, relating to the nozzles 18 arranged on the samestraight line, since the printing direction positions of the nozzles 18are different from each other, the data of the different time pointshould be for each nozzle 18, that is, each bit of the input serialdata. The above-described preprocessing concerns the operation of theorder of the bit data and the like.

In the tenth embodiment described hereinafter, the necessity of theabove-described preprocessing by an external controller, CPU or the likecan be removed, and by supplying only the serial data of the samecontents as those shown in FIGS. 33 and 34 to the ink jet print headdriver circuit, the printing by using the head of the inclined zig zagarrangement can be properly executed. As means for carrying out this,hardware for performing preprocessing is added to an ink jet print headdriver circuit. The tenth embodiment will now be described withreference to FIGS. 22 to 31.

In FIG. 22, there is shown the whole circuit construction of an ink jetprint head driver circuit of the tenth embodiment according to thepresent invention. This driver circuit is comprised of a clock generator84, an odd-even separator 86, an odd-side delay & multiplexer (MUX)88-0, an even-side delay & multiplexer 88-E, an odd-side (nozzle data)output circuit 90-0 and an even-side (nozzle data) output circuit 90-E.This driver circuit drives the head having the nozzles 18 arranged inthe inclined zig zag arrangement shown in FIG. 21. Also, the drivercircuit shown in FIG. 22 is implemented as an IC or an LSI. In thiscase, serial data F, a clock G, a printing direction signal a forexhibiting the head moving direction (printing direction), a latchsignal and a strobe signal are input to the driver circuit from theoutside, and the driver circuit outputs signals OUT1 to OUT48 for thepiezoelectric elements 30 of a certain number (=48) of dots.

In this embodiment, the head of the inclined zig zag arrangement can bedriven by inputting the similar data F and clock G as those of thecircuit shown in FIG. 35 except the printing direction signal a becausethe preprocessing for dealing with the inclined zig zag arrangement iscarried out in the driver circuit. By employing this construction, thereis no need to previously apply processing such as an order operation andthe like to the serial data F to be supplied, and the same usability asthat using the head having the nozzles arranged on one vertical straightline can be maintained. Further, since the head of the inclined zig zagarrangement is used, the density of the dots 24 can be raised.

Next, the parts of the driver circuit in this embodiment will now bedescribed in detail. As will be apparent from the following description,the driver circuit can be readily constructed by using one IC, and hencea reduction of a substrate occupied area and a low production cost canbe realized.

First, as shown in FIG. 23, the clock generator 84 is comprised of a Dtype flip-flop 92. In the D type flip-flop 92, a Q output is fed back toa D input, and the clock G is input to the CK terminal. Hence, when theclock G rises, the Q output and the Q output are inverted, and signalsG1 and G2 obtained as the Q output and the Q output become clocksobtained by two-dividing of the clock G. Thus, the clock G2 and theclock G1 become opposite phases. As described hereinafter, since theclock G1 is used for separating the data concerning the odd numbernozzle from the serial data F, the clock G1 is hereinafter referred toas an odd-side clock. Similarly, the clock G2 is used for separating thedata concerning the even number nozzle from the serial data F, the clockG2 is hereinafter referred to as an even-side clock.

As shown in FIG. 24, the odd-even separator 86 is comprised of outputgates 94 and 96, a clock selecting gate 98 and a shift register 100. Theoutput gate 94 outputs either the data F or data FD as odd-side data FOwhen the printing direction signal a is H or L. The output gate 96outputs either the data FD or the data F as even-side data FE when theprinting direction signal a is H or L. The clock selecting gate 98outputs either the even-side clock G2 or the odd-side clock G1 as ashift clock GO when the printing direction signal a is H or L. The shiftregister 100 shifts the data F every one bit at the timing of the shiftclock GO and outputs the data FD shifted 8×24 bits (=8 lines).

In this case, the data F0 and FE obtained in the odd-even separator 86are called the odd-side data and the even-side data, respectively,because, when these data are latched at the timing of the odd-side clockG1 or the even-side clock G2, data concerning the odd number or evennumber nozzle 18 (hereinafter referred to as odd-nozzle data FOm andeven-nozzle data FEm, respectively) are extracted.

When the printing direction signal a=H, the odd-side data FO are thedata F, and the even-side data FE are the data FD obtained by delayingthe data F 8×24 bits. At this time, since the data FD are obtained bythe shifting operation by using the even-side clock G2 in the shiftregister 100, their contents are the even-nozzle data. In turn, when theprinting direction signal a=L, the odd-side data FO are the data FD, andthe even-side data FE are the data F. At this time, since the data FDare obtained by the shifting operation by using the odd-side clock G1,their contents are the odd-nozzle data.

Further, in the shift register 100, the 8×24 bits of shift is carriedout. This means that the data FD are delayed by 8 lines compared withthe data F. That is, since the nozzles 18 are arranged in the inclinedzig zag arrangement, as shown in FIG. 21, and the numbers of the nozzles18 arranged on the two straight lines are 24, by the 8×24 bits of shift,8 lines are delayed. In this case, the line is the arrangement of thedots 24 in the direction perpendicular to the printing direction.

Therefore, the data FO and FE output from the odd-even separator 86 havethe contents Shown in FIG. 25. First, when the printing direction signala=H and an n-th line of data as the data F are input, the odd-side dataFO become the n-th line of data F and the even-side data FE become an(n-8)th line of data FD of 8 lines older than the data F. Next, when theprinting direction signal a=L and the (n+1)th line of data as the data Fare input, the odd-side data FO become an (n-7)th line of data FD andthe even-side data FE become the (n+1)th line of data F of 8 lines newerthan the data FD.

These odd-side and even-side data FO and FE having such contents alongwith the odd-side clock G1 and the even-side clock G2 are input to theodd-side delay & multiplexer 88-0 and the even-side delay & multiplexer88-E, respectively.

In FIGS. 26 and 27, there are shown the odd-side delay & multiplexer88-0 and the even-side delay & multiplexer 88-E, respectively.

The odd-side delay & multiplexer 88-0 is comprised of shift registers102-OH and 102-OL, multiplexers 104-01 to 104-024, shift registers106-01 to 106-023, a multiplexer 108-0 and an up/down counter 110-0.Similarly, the even-side delay & multiplexer 88-E is comprised of shiftregisters 102-EH and 102-EL, multiplexers 104-El to 104-E24, shiftregisters 106-El to 106-E23, a multiplexer 108-E and an up/down counter110-E. The differences between the odd-side delay & multiplexer 88-0 andthe even-side delay & multiplexer 88-E are as follows. First, the datato be processed are the odd-side data FO and the even-side data FE.Second, the clocks used for the processings are the odd-side clock G1and the even-side clock G2. Third, the output data are the odd-nozzledata FOm and the even-nozzle data FEm. Except for these differences, theodd-side delay & multiplexer 88-0 and the even-side delay & multiplexer88-E have almost the same internal construction and processing function.Hence, in this embodiment, only the odd-side delay & multiplexer 88-0will be described, and the description of the even-side delay &multiplexer 88-E can be omitted for brevity.

In FIG. 26, the odd-side data FO separated from the input data F in theodd-even separator 86 are input to the 24 bits of shift registers 102-0Hand 102-0L. The shift register 102-0H shifts the input odd-side data FOat the timing of the odd-side clock G1 to generate odd number nozzledata FOH. That is, the odd-side data FO output from the odd-evenseparator 86 are latched by the shift register 102-OH at the timing ofthe odd-side clock G1 to generate the odd number nozzle data FOH.Similarly, the shift register 102-OL shifts the input odd-side data FOat the timing of the odd-side clock Gi to generate odd number nozzledata FOL.

Hence, the odd number nozzle data FOH and FOL generated by therespective shift registers 102-OH and 102-OL become one line (24 bits ononly odd-side) of data of the same contents. However, the odd numbernozzle data FOH and the odd number nozzle data FOL are fed to differentparts. More specifically, the odd number nozzle data FOH, such as the24th bit to the multiplexer 104-024, the 23th bit to the multiplexer104-023, . . . , and the first bit to the multiplexer 104-01, areallocated to the targets in order of the shift bit number increase. Onthe other hand, the odd number nozzle data FOL, such as the first bit tothe multiplexer 104-024, the second bit to the multiplexer 104-023, . .. , and the 24th bit to the multiplexer 104-01, are allocated to thetargets in order of the shift bit number decrease. In other words, theodd number nozzle data FOH and FOL to be supplied to the multiplexers104-01 to 104-024 are the data whose bit orders are mutually inverted.

In this case, the multiplexers 104-01 to 104-024 are 2 to 1 multiplexersand thus function as selectors. The multiplexers 104-01 to 104-024select and output either the odd number nozzle data FOH or FOL when theprinting direction signal a is H or L. The bits output from themultiplexer 104-024 are shifted by 4×(24-1)=92 bits in the shiftregister 106-023 of its rear stage, and the bits output from themultiplexer 104-023 are shifted by 4×(24-2)=88 bits in the shiftregister 106-022. In this manner, the outputs of the multiplexers 104-02to 104-024 are shifted by (4×dot position) of bits in the shiftregisters 106-01 to 106-023. The output of the multiplexer 104-01 is notshifted. The outputs of the shift registers 106-01 to 106-023 and theoutput of the multiplexer 104-01 are input to the multiplexer 108-0. Inthis case, the shift registers 106-01 to 106-023 are reset at theoperation start time and the printing direction reverse time.

Thus, the odd number nozzle data shifted by the different bit numbersevery bit are multiplexed by the multiplexer 108-0 to convert into theserial data FOm of the equal rate to the odd-side clock G1. Themultiplexing direction in the multiplexer 108-0 is determined by theoutputs of the up/down counter 110-0. The up/down counter 110-0 countsthe odd-side clock G1 either up to 24 or down to 0 when the printingdirection signal a is H or L. As a result, when the printing directionsignal a is H, the counted result is input to the multiplexer 108-0 inorder of 1, 2, 3, . . . and 24, and, when the printing direction signala is L, the counted result is input in reverse order. The multiplexer108-0 selects and outputs the bit data of the output of the multiplexer104-01 and the outputs of the shift registers 106-01 to 106-023depending on the counted result of the up/down counter 110-0. Forexample, when the counted result input from the up/down counter 110-0 is1, the multiplexer 108-0 selects the output of the multiplexer 104-01and outputs the selected output, and, when the counted result of theup/down counter 110-0 is 2, the multiplexer 108-0 selects the Output ofthe shift register 106-01. Accordingly, the multi plexing order by themultiplexer 108-0 is changed depending on the printing direction.

FIG. 28 shows the meaning of the operation of the odd-side delay &multiplexer 88-0 and the even-side delay & multiplexer 88-E.

First, when the data are expressed as the positions of the dots 24, theodd-side data FO output from the odd-even separator 86 include the bitat a corresponding to the dots 24 on a straight line shown by a brokenline 112. Similarly, the even-side data FE output from the odd-evenseparator 86 include the bit data corresponding to the dots 24 on astraight line shown by a broken line 114. The line 112 of the odd-sidedata FO and the line 114 of the even-side data FE are separated by, 8lines, and this interval is obtained by the delay processing in theodd-even separator 86.

The nozzles 18 have the inclined zig zag arrangement shown in FIG. 21,as described above. In this arrangement, the printing direction intervalbetween the two lines of nozzle arrangement is equivalent to 8 dots.Hence, when the printing from the left hand sine to the right hand sideis executed, the odd-side data FO of the line 112 should be 8 linesolder than the even-side data FE of the line 114, and in the oppositecase, the even-side data FE should be 8 lines older than the odd-sidedata FO. The above-described 8 lines delay principle in the odd-evenseparator 86 is used for adapting the printing control to thegeometrical relationship between the arrangement lines of the nozzles18.

Further, in the odd-even separator 86, the target of the 8 line delayprocessing is changed depending on the value of the printing directionsignal a. In the case of printing from the left hand side to the righthand side, that is, the printing direction signal a=H, the line 112concerning the odd-side data FO is positioned behind the line 114concerning the even-side data FE along the printing direction. On theother hand, in the case of printing from the right hand side to the lefthand side, that is, the printing direction signal a=L, the line 112concerning the odd-side data FO is positioned in front of the line 114concerning the even-side data FE along the printing direction. Asdescribed above, which data FO or FE should be set to the new data isdetermined depending on the printing direction, that is, the value ofthe printing direction signal a. The target selection processing for the8 lines delay processing depending on the value of the printingdirection signal a in the odd-even separator 86 is used for adapting theprinting control to such an ahead and behind relation.

In the odd-side delay & multiplexer 88-0, the odd-side data FOselectively delayed depending on the interval between the straight linesand the printing direction are latched at the timing of the odd-sideclock G1 in the shift registers 102-OH and 102-OL. By this operation,the odd number nozzle data FOH and FOL shown by white dots on the brokenline 112 or 114 are produced from the odd-side data FO.

Similarly, in the even-side delay & multiplexer 88-E, the even-side dataFE selectively delayed depending on the interval between the straightlines and the printing direction are latched at the timing of theeven-side clock G2 in the shift registers 102-EH and 102-EL. By thisoperation, the even number nozzle data FEH and FEL shown by black dotson the broken lines 112 and 114 are produced from the even-side data FE.

In the odd-side delay & multiplexer 88-0, further, the odd number nozzledata FOH and FOL are delayed in the shift registers 106-01 to 106-023.This operation delays the bit data depending on the positions of thedots 24 on a broken line 116. The broken line 116 corresponds to thestraight line of the odd number nozzles 18 shown in FIG. 21.

Similarly, in the even-slide delay & multiplexer 88-E, the even numbernozzle data FEH and FEL are delayed on the shift registers 106-El to106-E23. This operation delays the bit data depending on the positionsof the dots 24 on a broken line 118. The broken line 118 corresponds tothe straight line of the even number nozzles 18 shown in FIG. 21.

For example, the first dot 24 positioned on the broken line 116corresponds to the first nozzle 18 in FIG. 21, and the third dot 24positioned on the broken line 116 corresponds to the third nozzle 18 inFIG. 21. The first nozzle 18 and the third nozzle 18 are arranged on thesame straight line, as shown in FIG. 21, and the printing directioninterval of these nozzles 18 is equivalent to 4 dots. Hence, the bitdata to be used for the ink discharge control (output) by the firstnozzle 18 at a certain printing timing must be data at a timing with 4dots difference with respect to the bit data to be used for the inkdischarge control (output) by the third nozzle 18. In the case of theprinting direction signal a=H, that is, the printing direction is fromthe left hand side to the right hand side, the former must be older datathan the latter, and in the case of the printing direction signal a=L,that is the printing direction is from the right hand side to the lefthand side, the former must be newer data than the latter. The shiftregisters 106-01 and 106-El perform this timing control processing, thatis, the 4 bits-per-one-interval delay processing depending on thepositions of the nozzles 18 on the same straight line. The other shiftregisters 106-02 to 106-023 and 106-E2 to 106-E23 carry out the similarprocessing.

Also, in the odd-side delay & multiplexer 88-0 and the even-side delay &multiplexer 88-E, there are provided the two shift registers 102-OH and102-OL as a shift register 102-0 and the two shift registers 102-EH and102-EL as a shift register 102-E, and further the multiplexers 104-01 to104-024 and 104-El to 104-E24 for selecting these outputs and theup/down counters 110-0 and 110-E are provided so as to cope with thechange of the positional relationship (ahead or behind of the printingdirection) between the nozzles 18 arranged on the same straight linedepending on the printing direction.

For example, the third nozzle 18 is positioned either behind or in frontof the first nozzle 18 when the printing direction signal a is H or L.In this embodiment, depending on H or L of the printing direction signala, the different bit order of odd number nozzle data are selected andare delayed corresponding to the positions of the nozzles 18 arranged onthe same straight line by the shift registers 106-01 to 106-023. Theformation of the different bit order of odd number nozzle data isexecuted by the shift registers 102-0H and 102-OL, and their selectionsare carried out by the multiplexers 104-01 to 104-024. Further, theobtained odd number nozzle data are multiplexed in order depending onthe printing direction, and the obtained odd-nozzle data FOm are outputto the odd-side output circuit 90-0 in order of the numbers attached tothe nozzles 18 shown in FIG. 21. Also, on the even-side, the operationis carried out in the same manner as described above in the even-sidedelay & multiplexer 88-E.

As described above, the odd-side delay & multiplexer 88-0 and theeven-side delay & multiplexer 88-E form the data suitable for the headof the inclined zig zag arrangement shown in FIG. 21 by using theodd-side data FO and the even-side data FE output from the odd-evenseparator 86.

In FIGS. 29 and 30, there are shown the odd-side output circuit 90-0 andthe even-side output circuit 90-E. As shown in FIGS. 29 and 30, theconstructions of the odd-side output circuit 90-0 and the even-sideoutput circuit 90-E are the same as the driver circuit for one verticalarrangement of the nozzles as shown in FIG. 35, except that the outputbit number of each circuit is 48/2=24 bits because of the twoarrangements of the nozzles 18. In this embodiment, the odd-side outputcircuit 90-0 is comprised of a 24 bits of shift register 25-0, a 24 bitsof latch 26-0 and 24 ANDs 28-0. Similarly, the even-side output circuit90-E is comprised of 24 bits of shift register 25-E, 24 bits of latch26-E and 24 ANDs 28-E. To the odd-side output circuit 90-0, the odd-sideclock G1 and the odd-nozzle data FOm are input, and the odd-side outputcircuit 90-0 outputs 24 odd number OUT1, OUT3, . . . and OUT47. To theeven-side output circuit 90-E, the even-side clock G2 and even-nozzledata FEm are input, and the even-side output circuit 90-E outputs 24even number OUT2, OUT4, . . . and OUT48.

In FIG. 31, there is shown one embodiment of a circuit to be used forthe shift registers 106-01 to 106-023 or 106-E1 to 106-E23. The circuit120 is a circuit for one bit shift, and thus depending on a shift bitnumber, a plurality of circuits 120 can be connected in cascade so as toobtain a shift register of the desired bit number.

The circuit 120 is comprised of six transistors Tr1 to Tr6. The bit datato be shifted are applied as a voltage to the gate (G) of the transistorTr1, and the electric charge is stored in the capacitance between thegate (G) and the source (S) of the transistor Tr1. When the clock G1 ischanged to H, the transistor Tr1 acts as an inverter, and, when the gate(G) voltage is high or low, a drain (D) voltage becomes low or highrespectively. In the case of the high drain (D) voltage, by thisvoltage, the electric charge is stored in the capacitance between thegate (G) and the source (S) of the transistor Tr4. The transistor Tr4operates in the same manner as the transistor Tr1 by the clock G2 havingthe opposite phase to that of the clock G1. Hence, in this circuitconstruction, the shifting of the bit data can be performed and the highspeed operation can be carried out because of the serial connection ofthe dynamic gates.

In this embodiment, further, the shift registers 106-01 to 106-023 and106-El to 106-E 23 can be constructed by using a RAM. That is, aplurality of RAMs are connected in cascade so that 4 bits of data may betransferred from the front stage to the rear stage and store the datatherein. This can be suitably used for processing the delay per 4 bitunits in this embodiment. When the shift register is constructed byusing the RAMs, the data transfer is executed by using the flip-flop orthe like, and it is sufficient to use a certain cycle of the clock as awrite enable of the RAMs.

As described above, in this embodiment, the input serial data areseparated into the odd-side serial data FO and the even-side serial dataFE, and the serial data FO and FE are delayed depending on the positionsof the nozzles 18 arranged in the inclined zig zag arrangement in thehead and the printing direction signal a. Hence, by inputting the dataand the like similar to the case of the vertical arrangement of thenozzles 18, the printing can be executed without preprocessing the orderoperation or the like. As a result, the usability can be improved.Further, in particular, by constructing using the IC, the circuitstructure of the ink jet printer can be simplified, and thus a reductionof substrate occupied area and low cost can be realized.

Further, the delay amount setting depending on the interval between thenozzle arrangements and the interval between the nozzles 18 arranged onthe same straight line is switched depending on the printing directionsignal a, and with this operation, the orders of the serial/parallelconversion by the shift registers are switched by the switching of themultiplexing direction. Hence, the printing control depending on theprinting direction can be carried out. Also, since the two-phase clocksG1 and G2 for executing the odd-even separation can be generated by asimple circuit as shown in FIG. 23, it is sufficient to use a clocksimilar to a conventional clock as the original clock G. Further, sincethe operations such as the delay, the multiplexing, the serial/parallelconversion and the output are executed by the circuit structure of twosystems such as odd and even sides, the circuit construction can beseparated into units and thus can be simplified.

Further, this embodiment can be combined with any of the fifth to eighthembodiments. Also, as described above, the sixth to eighth embodimentscan be combined with the second embodiment. When the second embodimentis combined with any of the sixth to eighth embodiments and the tenthembodiment, since the nozzles are classified into a plurality of groups,it is required to modify some parts such as providing a plurality ofcircuits shown in FIG. 22 and the like according to the nozzle grouping,but such modifications are apparent for those skilled in the art.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not to be restricted by thoseembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

What is claimed is:
 1. A head for ink jet printing comprising:a substrate; a plurality of nozzles arranged on a flat surface of the substrate for discharging ink, the nozzles being arranged in a zig zag arrangement wherein the nozzles are arranged in only first and second straight lines on the flat surface, and wherein the nozzles arranged in the first straight line are offset with respect to the nozzles arranged in the second straight line along a direction perpendicular to a printing direction; and path means formed in the substrate for supplying the ink to the nozzles, the path means including: a plurality of pressure chambers formed in the substrate, and a plurality of ink slits, having a substantially narrower width than the pressure chambers, formed in the substrate and arranged radially, each ink slit fluidly coupling one of the pressure chambers to one of the nozzles, wherein the ink slits have lengths that are similar so that a viscous drag for ink passing through the ink slits is equalized among the ink slits; wherein a depth of each ink slit is larger than a width of each ink slit at a location near the nozzles.
 2. The head of claim 1, wherein the path means further includes:an ink introducing mechanism for introducing the ink into the pressure chambers;and discharge means for discharging ink and including a plurality of pressing elements attached on the substrate at location corresponding to the pressure chambers for applying a pressure to a corresponding pressure chamber in response to a command, wherein the pressing element receives the command and applies the pressure to the corresponding pressure chamber the ink within the corresponding pressure chamber to be fed to the corresponding ink slit, and the corresponding nozzle to discharge the ink, wherein when the command is released, almost the same amount of ink as the amount of ink fed to the corresponding ink slit is introduced into the corresponding pressure chamber by the ink introducing mechanism.
 3. The head of claim 2, wherein the ink introducing mechanism includes:an ink chamber formed to connect and surround the pressure chambers on the substrate; and an ink introducing aperture for introducing the ink into the ink chamber.
 4. The head of claim 2, wherein the substrate is a photosensitive glass substrate, and the nozzles, the ink slits, the pressure chambers and the ink introducing mechanism are formed by an anisotropic etching of the substrate.
 5. The head of claim 4, wherein the nozzles are formed by the anisotropic etching including a step of exposing while the substrate is rotated and inclined.
 6. The head of claim 2, wherein the nozzles are separately arranged in a plurality of groups near a central point of either a circle or a circular arc on the flat surface.
 7. The head of claim 6, wherein a plurality of groups of the pressure chambers and the ink slits corresponding to the plurality of groups of nozzles constitute a plurality of ink paths mutually separated.
 8. The head of claim 6, wherein the separation groups of the nozzles are three.
 9. The head of claim 7, wherein different color inks are supplied to the respective ink paths.
 10. The head of claim 2, wherein the pressing elements are piezoelectric elements that are excited and distorted by the command supplied as a voltage.
 11. The head of claim 10, wherein the discharge means includes a vibrating member to be vibrated by the distortion of the piezoelectric elements when the piezoelectric elements are excited.
 12. The head of claim 2, wherein the discharge means includes the piezoelectric substrate in a circular arc, the piezoelectric substrate having a common electrode on one surface and a plurality of individual electrodes corresponding to the pressure chambers on another surface, and wherein each pressing element is a piezoelectric element composed of the piezoelectric substrate, each individual electrode and the common electrode.
 13. The head of claim 12, wherein the piezoelectric substrate includes concav surfaces for electrically and acoustically separating the adjacent individual electrodes.
 14. The head of claim 12, wherein the piezoelectric substrate is arranged so that the individual electrodes mounted on another surface of the piezoelectric substrate face the opposite side to the pressure chambers.
 15. The head of claim 1, wherein each nozzle posesses a substantially circular opening.
 16. The head of claim 1, wherein there is a plurality of separated groups of nozzles arranged in the zig zag arrangement, the groups being coupled to a respective ink source of a different color. 